Sound pickup assembly for an acoustic string instrument and including a foam pad element supporting microphones

ABSTRACT

A sound pickup assembly for an acoustic string instruments includes a pad element of foam material and shaped to be placed in an interference fit into a sound hole of the instrument. The foam pad element has therein openings for microphones and leads, with the microphones being positioned inside the foam pad element in a manner such that the sound waves inside the resonator body of the instrument may readily strike the surfaces of heads of the microphones without interference.

BACKGROUND OF THE INVENTION

The present invention relates to a pickup assembly including at leasttwo microphones for acoustic string instruments, particularly foracoustic guitars.

Prior pickup devices of this kind usually include microphone holdingmeans to be affixed to the external surface of the acoustic guitar. Ithas been known also to install microphones inside the resonator cavityof a guitar. For picking up sound, it is important to attenuatefrequencies at the lower end of the medium range of audio frequencies.Without such attenuation the instrument's inherent resonance may peak tomore than 30 db. High-sensitivity microphones are expensive and provideno satisfactory solution to the problem. Acoustic guitars having aninherent resonance near the lower end of the medium frequency range(about 150 to 300 Hz) are commercially available in a broad range ofqualities.

SUMMARY OF THE INVENTION

The object underlying the present invention is to provide a sound pickupassembly of the aforesaid type which is suited for cost-effectivelarge-scale production and is universally applicable to acoustic stringinstruments of virtually any tape, and particularly to all types ofacoustic guitars, and which in particular provides for attenuation so asto linearize the frequency response. In addition, the pickup device ofthe present invention is intended to be easily and quickly manipulable.In accordance with the invention, this object is achieved by a pad offoam material which has guide openings extending therethrough formicrophones and connecting leads, and which is adapted to be mountedinside the sound hole of the instrument with its outwardly directed endface extending flush with the resonator body of the instrument, with themicrophones being adapted to be positioned inside the foam pad in amanner such that the sound waves inside the resonator body of theinstrument may without interference strike the surface of eachmicrophone head.

Advantageous further developments of the inventive pick-up assembly arerecited in the dependent claims.

The inventive pickup assembly ensures excellent attentuation of theinstrument's inherent resonance as the foam material acts to linearizethe frequency response at the lower end of the medium frequency range.The foam pad may consist of any suitable damping material; however, itis preferred to use foamed plastics. The foam pad is designed to bemanually inserted in position in an interference fit in the sound holeof the instrument and ensures positive placement of the microphone leadsand secure retention of the microphones. In the inventive assembly, themicrophones may be most simple in construction and quality withoutsacrificing frequency response linearity. The inventive sound pickupassembly is suited in general for a wide variety of acoustic stringinstruments and particularly for acoustic guitars of all kinds. Also,the inventive sound pickup assembly lends itself to mass production in acost-effective manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of a preferred embodiment of the inventivesound pickup assembly is with reference to the attached drawingswherein.

FIG. 1 is a plan view of a guitar having the inventive pick-up assemblyinstalled in the sound hole thereof, and

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a plan view of an acoustic guitar 1 having foam pad element3 fitted and clamped in place in sound hole 2. Attention is directedalso to the section view shown in FIG. 2 and taken generally along line2--2 of FIG. 1. Outwardly directed end face 4 of foam pad element 3,generally cylindrical as seen in FIG. 1, extends substantially flushwith the outer surface 5 of resonator body 6 of guitar 1. In thiscondition, the pad extends through the entire depth of resonator body 6down to its bottom 7. The inherent resilience of foam pad 3 fitted intosound hole 2 causes foam pad 3 to be seated and retained firmly in aninterference fit in position between the edges of the sound hole andbottom 7. In this position, bottom surface 8 of short end section 9 offinger board 10 of guitar 1, which short end section may project a shortdistance into sound hole 2, additionally secures pad 3 in place againstaccidental dislocation.

An external lead 11 is run laterally of strings 13 of guitar 1, whichstrings extend along finger board 10 to bridge 12, into a short guidepassage 14 extending axially downwardly, through approximately half theheight of the pad, from end face 4 of pad 3 merging into two enlargedopenings 15, 16 at opposite sides of the outer peripheral surface 17 offoam pad 3 inside resonator cavity 18 of guitar 1. Openings 15, 16receive respective microphones 19, 20 in a manner such that the soundwaves inside resonator body 6 may without interference strike surface21, 22, of respective of microphone heads 25, 26. At the lower end ofpassage 14, lead 11 splits into two separate leads 23, 24 each of whichcontinues to extend through respective enlarged openings 15, 16 to makeconnection to an respective microphones 19, 20. A disc made of feltmaterial may be placed on surface 4 of foam pad 3 fitted into sound hole2 to provide a completely planar and flush termination with the topsurface 27 of resonator body 6 of guitar 1.

What we claim is:
 1. A sound pickup assembly for an acoustic stringinstrument having a resonator body including an outer surface throughwhich a sound hole extends and a bottom surface spaced from the outersurface, said assembly comprising:a resilient pad element of foammaterial adapted to be resiliently seated in the resonator body betweenthe outer surface and the bottom surface and extend into the sound holethereof, said pad element having an end face and an outer peripheralsurface extending from said end face, the end face terminating generallyflush with the outer surface of the resonator body and the outerperipheral surface facing the inside of the resonator body with the padelement seated, and guide openings extending therein for receipt ofmicrophones and leads; and microphones extending in the guide openingsfor picking up sound waves in the resonator body, said microphoneshaving respective heads positioned within the resonator body in a mannerin which the sound waves inside the resonator body strike the headswithout interference when the pad element is seated within the body. 2.A sound pickup assembly as claimed in claim 1, wherein said foam padelement comprises a material acting to substantially attenuatefrequencies at the lower end of the medium frequency range.
 3. A soundpickup assembly as claimed in claim 1, wherein said foam pad element iscylindrical in shape, and said guide openings comprise a first guidepassage extending axially through approximately half the height of saidcylindrical element and merging at an inner end thereof with a secondguide passage extending through said cylindrical element diametricallythereof.
 4. An acoustic string instrument comprising:a resonator bodyincluding an outer surface through which a sound hole extends and abottom surface spaced from the outer surface; a pad element of foammaterial extending across the sound hole and having an end faceterminating generally flush with the outer surface thereat, an outerperipheral surface extending from the end face into the resonator bodyand guide openings extending therein for receipt of microphones andleads; and microphones extending in the guide openings for picking upsound waves within the resonator body, said microphones havingrespective heads positioned within the resonator body in a manner inwhich the sound waves inside the resonator body strike the heads withoutinterference.